Preparation And Properties Of Modified Polyacrylonitrile/Titanium Dioxide Porous Photocatalytic Fiber

Titanium dioxide(TiO₂)has excellent photocatalytic properties and easy to obtain,so it is widely used in the field of water pollution treatment.However,it has many defects in practical industrial applications.The main reason is that TiO₂has a wide band gap,which can only have light response when excited by ultraviolet,and has poor utilization of solar energy.In addition,TiO₂has problems such as difficulty in recycling after use in a liquid phase system.In view of the above problems,this thesis starts from the research of TiO₂loading and doping modification.By using polyacrylonitrile(PAN)as the carrier,and polyvinylpyrrolidone(PVP)as the porogen,changing raw material ratio developed the PAN/TiO₂porous photocatalytic fiber with a large specific surface area and porous morphology.The second is to use homemade nitrogen-doped graphene(NG)modified TiO₂to prepare a narrower band width modification NG-TiO₂.NG-TiO₂makes light absorption edge redshift and can be excited under visible light to improve the photoactivity of TiO₂.Electrospinning technology is used to load it then obtained a photocatalytic fiber with reusability under visible light conditions,providing a feasible method for practical applications.In this thesis,methylene blue(MB)aqueous solution is selected as the target degradation product,and the adsorption-catalytic performance and reusability of photocatalytic fibers under xenon lamp irradiation are explored,and the following conclusions are obtained:1.In the electrospinning system composed of PAN,PVP,and TiO₂,when the PAN spinning concentration is 8 wt%and the PVP is 8 wt%,the TiO₂loading is 4 wt%,the photocatalytic fiber with a disordered porous structure on a single fiber was prepared.Photocatalytic fiber specific surface area is 64.12 m²/g,which is 4.5 times higher than PAN pure membrane,and its average diameter is 490 nm.The adsorption-catalytic performance test results of the photocatalytic fiber showed that the degradation rate is reaching 97.43%when the MB solution is 20 mg/L,the photocatalyst addition is 2 g/L,with UV lamp lighting for 120 min.After 5 times of repeated use,the photocatalytic efficiency can still reach more than 90%.2.Using urea and self-made graphene oxide(GO)as raw materials,NG with a lamellar structure was prepared by hydrothermal method,then it was further hydrothermally reacted with TiO₂at 180?for 12 h to prepare NG-TiO₂,it shows that the minimum band gap of NG-TiO₂prepared at 15 wt%is 2.69 e V,which is significantly reduced compared to 3.16 e V of TiO₂,so that NG-TiO₂can be excited by visible light.3.The adsorption-catalytic performance of the photocatalytic fiber under different loading amount of NG-TiO₂was investigated,the results show that when the loading of NG-TiO₂is5 wt%,the degradation rate of photocatalytic fibers under visible light irradiation can reach93.36%.After 5 times of repeated use,the degradation rate can still reach more than 85%.The Langmuir-Hinshelwood model was used to describe the first-order degradation kinetics of the photocatalytic fiber.It was found that when the loading of NG-TiO₂was increased from 3 wt%to 5 wt%,the degradation rate increased from 82.03%to 93.36%,and the first-order rate constant increased from 1.273×10^-2min^-1increased to 2.241×10^-2min^-1.